Collapsible antenna support for aircraft microwave landing systems



y 1954 F. L. HAGGERTY 2,683,011

COLLAPSIBLE ANTENNA SUPPORT FOR AIRCRAFT MICROWAVE LANDING SYSTEMS FiledFeb. 15, 1951 2 Sheets-Sheet l INVENTOR. FEBNC'AS L, H66 EE 7') July 6,1954 F. 1.. HAGGERTY COLLAPSIBLE ANTENNA SUPPORT FOR AIRCRAFT MICROWAVELANDING SYSTEMS 2 Sheets-Sheet 2 Filed Feb. 13 1951 nTTo h/EY FIZE/VF Wm N 4 M 14 g M L m .0 Mw mw n fln/ W w 3 E E V 5 Z w ofi MM 8 0/ :0 ermm Km 5 Patented July 6, 1954 UNITED STATES PATENT OFFICE COLLAPSIBLEANTENNA SUPPORT FOR AIR- CRAFT MICROWAVE LANDING SYSTEMS Francis L.Haggerty, St. James, N. Y., assignor to the United States of America asrepresented. by the Secretary of the Air Force Application February 13,1951, Serial No. 210,738

. 6 Claims. 1

The present invention relates to a collapsible antenna support for usein an aircraft microwave landing system.

The primary object of the invention is to provide a supporting structurefor a microwave antenna or radiator in which a simple framework includesat least one frangible joint adapted to fracture in case the antenna orframework is struck by an aircraft, whereby the framework immediatelycollapses to avoid interrupting continued movement of the aircraft.

A further object of the invention is to provide an antenna supportingstructure comprising a framework in which several elongated framemembers are pinned or bolted together in such a manner that shearing orfracture of a joint will allow the whole framework to collapse by apivoting movement about other joints not susceptible to fracture.

Another object of the invention is to provide an antenna supportingstructure for a microwave antenna particularly intended for locationnear one end of an aircraft runway and to provide such a supportingstructure including a pair of side frames of triangular form made byconnecting three bars at their ends by bolts and to provide at the upperapex thereof a frangible bolt adapted to fracture in case the antenna orsupporting structure is struck by an aircraft, so that the triangularend frames will collapse without further interrupting movement of theaircraft and without causing serious damage to the aircraft. I

Another object of the invention is to provide an antenna supportingstructure for a microwave antenna particularly intended for use in anaircraft microwave landing system and to include in the supportingstructure means for quickly and easily varying the angular dispositionof the antenna with respect to the plane of the aircraft landing strip;

Another object of the invention is to generally improve the antennasupporting structure for the directive antenna as disclosed in thepatent to G. B. Litchford et al. No. 2,513,338, granted on July 4, 1950.I

The above and other objects of the invention will become apparent uponreading the following detailed description in conjunction with theaccompanying drawings, in which:

Fig. 1 is a side elevation view of the present antenna supportingstructure.

Fig. 2 is a rear elevation view of the present antenna supportingstructure but with the wave modulator and wave guide removed.

Fig. 3 is a plan view of the aircraft runway and associated microwavelanding system.

In the patent to Litchford et a1. referred to refinements in thesupporting framework for the antenna. The radiator should include theconcave reflector and pair of cylindrical parabolas secured thereto asshown in the patent to Litchford et al., although in the presentdescription only the reflector will be referred to.

Fora description of the invention, reference is made to Figs. 1 and 2wherein there is shown a concrete slab or sub-base l, the upper surfaceof which is preferably flush with the ground or even a little belowground level. Mounted thereon in any suitable manner is a pair ofsimilar and parallel timbers 2 and 3 which support another pair oftimbers 4 and 5 bridging the space between the foundation timbers 2 and3. Laid along the upper surfaces of the base timbers 4 and 5 arehorizontal angle irons 6 and i about the same length as the timbers 4and 5. Fixed to the remote vertical sides of these timbers are shortupright angle irons 8 and 9 joined by a transverse angle iron Ill boltedat opposite ends to flanges of the members 8 and 9 and bearing on theupper edges of the angle irons 8 and l. Inwardly extending adjustingscrews II extend through the members 8 and 9 and bear on the uprightflanges of angle irons 6 and l to provide for limited crosswiseadjustment of the antenna supporting framework after the installationhas been completed. The base members 6 and I may be fastened down to thetimbers 4 and 5 respectively after the structure is completed andproperly adjusted, such fastening being accomplished by lag screwspassing through the horizontal flanges of angle irons 6 and 1. At theforward ends of members 6 and 7 there are similar uprights l2 and I3pivotally mounted thereon by bolts l4. Similar bolts 15 serve topivotally mount sloping members It and ii, connected to uprights I 2 andI3 by light duty shearable bolts [8. and l! are angle irons of a typesimilar to the base members 6 and 1. The upright members I2 and I3 arejoined by the transverse cross plate l9 having end flanges 20 and 2!extending forwardly, as seen in Fig. l. Noting Fig. 2 of the drawings,the transverse plate 19 extends outwardly of the members [2 and is toform side projections therefrom. Another rigidifying bar or plate 22connects the members [2 and 13, as

The frame members l2, I3, {6'

by welding, and there is a diamond-shaped frame of light bars 23 to 2Bwelded to the members [2, l3, l9 and 22, as shown in Fig. 2. Welded tothe sloping members 12 and [3 in bridging relation is a bar or plate 21.

Supporting elements are provided near the lower end of sloping members16 and I! to mount a wave modulator 28 receiving microwave energy by wayof wave guide 29. The modulated energy is conducted from the modulator2B to the reflector 30 by way of wave guide 3|. One or more separablejoints are provided in the wave guide 3|, as at 32. Extending upwardlyin a sloping manner from the lower ends of members i8 and H are angleirons 33 and 34 joined at their upper ends by a bar or plate 35. A pairof transverse angle irons 36 and 31 welded to the members It, I! and 33,34 serve to carry a base 38 secured to the modulator 28. The adjacentmembers It and 33 and I1 and 34 are connected by bars 39 which are alsowelded to angle irons 35 and 31.

Each of the uprights l2 and 13 carries an elongated angle bracket 40bolted to the associated uprights with wood strips 4| therebetween.E'ach bracket is provided with a slot 42 to slidably receive a pin 43carried at the lower end of a long channel iron 44, the web of which isat the forward side to provide a mounting surface for antenna supportingframe 45. Below the upper end of each channel iron 44 a pivot 45 servesto mount a link 4']. The upper end of each link 41 is mounted on atransverse shaft 48 and keyed thereto. The opposite ends of the shaftare journaled in friction-type bearing members as bolted on the remotefaces of flanges 29 and ill (see Fig. 2). Thus the similar links 'llrotate together and tend to stay in any adjusted position by reason ofthe frictional drag of the bearing assemblies 49. Adjustment of thelinks and consequent adjustment of the angular setting of the reflector30 is effected by means of screws 59 threaded through the webs ofchannel irons 44 and bearing on the links below the shaft 48. As may beseen in Fig. l the rim of reflector 30 is slightly off the true verticalbut by adjusting the screws 50 toward the links 4'5 the angularity ofthe reflector 30 with respect to vertical may be reduced.

The antenna supporting frame 45 comprises a ring section 51 havingvarious rods 52 to SI welded thereto and to a hoop 62 secured to thereflector 30 by brackets 63. Adjustably mounted atop the hoop 62 is atheodolite 64 for accurately lining the antenna up with respect to thelanding strip or runway. As may be seen in Fig. 3, the microwaveradiator is set up on the longitudinal axis of the runway at a distancefrom one end of the runway. The wave guide 2% extends laterally from therunway axis to a microwave station, set perhaps two hundred feet off theaxis.

For a consideration of the mode of operation of the invention it may beassumed that an aircraft is making a landing in the direction of arrow A(Fig. 3) on the runway. Should the brakes fail or for some other reasonthe aircraft rolls off the runway directly toward the microwaveradiator, the undercarriage or possibly the nose of the aircraft willstrike the radiator. In usual practice the top of the reflector 3!! isabout six feet above the ground level. This sudden blow will stress thewhole radiator structure but the weakest part is the shearable bolts 18at the apex of the supporting framework. Therefore these bolts willfracture. and the uprights I2 and it will pivot rearwardly about bolts Ii at their lower ends. As the uprights rotate rearwardly and downwardly,the opposite extending ends of the plate l9 serve as abutment membersand will contact the forward edges of brace members it and ll which arein pivotal path of the abutment members and thus cause these members toalso rotate rearwardly. The forward supporting members or uprights actto push the other s1 porting members, including the attached modulator,rearwardly and finally downwardly so that the whole structure folds upor collapses. As can be seen in Fig. 1, the base angle irons 6 and 7 jutout beyond the ends of the base timbers 4 and 5 at the rearward ends, sothat the interconnected members l6, ll and 33, 3d free to drop down tothe ground level. Of course the collapsing of the supporting structurecauses various joints in the wave guide to come apart and other damage,such as possible bending of the reflector 30, but the important factoris the damage caused to the aircraft itself. With the invention heredisclosed the supporting structure and elements carried thereby areadapted to collapse onto the ground and thus present much less of anobstruction to the aircraft so that the craft can roll on over thecomplete microwave radiator with a minimum of damage thereto. Practicehas shown that the collapsible an ha support has functioned very welland has prevented serious damage to large aircraft on more than oneoccasion.

While it is true that overrunning the runway on landing is the mostlikely occurrence whereby the antenna will be struck, it has been foundthat aircraft coming in for a landing in a direction opposite to that ofarrow A may also strike the antenna structure. In this case the initialforce may be applied to the sloping brace men bers I6 and I! but afterfracture of the small shear bolts or pins I8, the members it and H willcontact the ends of plate 19 and thus push the upright forward portionsof the antenna structure forwardly. When the antenna is struck by anaircraft which is still airborne the collapsing of the structure willenable the aircraft to clear the obstruction very nicely, even thoughthe initial impact may possibly damage a tire of the aircraftundercarriage.

The relative size and strength of the antenna parts and supportingstructure may be varied within wide limits but the suggested size of theangle irons is two or three inches across the flanges. The shearablebolts It; may be of mild steel, aluminum or brass and should not begreater than three-eighths of an inch in thickness. If a mild steel boltis chosen the size suggested is one-quarter inch. Until the antenna isstruck by an aircraft the only important stresses thereon are those dueto winds, so the relative strength of the supporting structure should bedesigned with wind velocities of a particular location in mind. Theadjustment of the reflector by the use of the adjusting screws 5c isanother important feature but one which seems to require no furtherelaboration.

The embodiments of the invention herein shown and described are to beregarded as illustrative only and it is to be understood that theinvention is susceptible of variations, modifications and changes withinthe scope of the appended claims.

I claim:

1. An antenna supporting structure for a microwave radiator comprising,a pair of elongated spaced apart parallel base members,

a pair of upright antenna supporting mem bers pivotally mounted at oneend of said base members, transverse members rigidly connecting saidpair of upright members, a pair of brace members pivotally mounted atthe other end of said base members and extending to the upper ends ofsaid upright members, shearable bolts serving to connect theintersecting upper ends of said upright members and said brace members,an antenna mounting ring secured to said upright members andsubstantially parallel thereto, struts rigidly connected to said ringand extending away from said upright members, and a hoop rigidlyconnected to said struts and adapted to receive the convex side of aparabolic microwave reflector.

2. An antenna supporting structure for a microwave radiator comprising,a pair of elongated spaced apart base members, a pair of upright antennasupporting members pivotally mounted at one end of said base members, atransverse member rigidly connecting said pair of upright members closetothe upper ends thereof, means to brace said upright members and retainthem in a predetermined upright position, separate bearing means mountedon opposite ends of said transverse member, a shaft extending throughsaid separate bearing means, a pair of links keyed to said shaft andextending downwardly in the same plane, an upright channel memberpivotally mounted on the lower end of each link, means providing asliding connec tion between the lower end of each channel member and acorresponding one of said upright members, means to adjust the angularrelation between said pair of links and the corresponding channelmembers, and means formounting a parabolic microwave reflector on saidchannel members.

3. An antenna supporting structure for a microwave radiator comprising,a pair of elongated spaced apart base members, a pair of upright antennasupporting members pivotally mounted at oneend of said base members, atransverse member rigidly connecting said pair of upright members closeto the upper ends thereof, a pair of brace members pivotally mounted atthe other end of said base members and extending to the upper ends ofsaid upright members, shearable bolts serving to connect theintersecting upper ends of said upright members and said brace members,separate bearing means mounted on opposite ends of said transversemember, a shaft extending through said separate bearing means, a pair oflinks keyed to said shaft and extending downwardly in the same plane, anupright channel member pivotally mounted on the lower end of each link,means providing a sliding connection between the lower end of eachchannel member and a corresponding one of said upright members, means toadjust the angular relation between said pair of links and thecorresponding channel members, and means for mounting a. parabolicmicrowave reflector on said channel members.

4. An antenna supporting structure for a microwave radiator comprising,a pair of elongated spaced apart base members, a pair of substantiallyvertical antenna supporting members pivotally mounted at one end of saidbase members, transverse members rigidly connecting said pair ofsubstantially vertical members, abutment means extending from therespective sides of said supporting members in substantially transversealignment, a pair of brace members pivotally mounted at the other end ofsaid base members and extending to the upper ends of said substantiallyvertical members in the pivotal path of the abutment means, andshearable bolts serving to connect the intersecting upper ends 'of saidsubstantially vertical members and said brace members,'whereby onshearing of the bolts the supporting members pivot, the abutment meanspivoting therewith, engaging the brace members to collapse thesupporting structure.

5. An antenna supporting structure for a microwave radiator comprising apair of elongated spaced apart base members, a pair of upright antennasupporting members pivotally mounted at one end of said base members, atransverse member rigidly connecting said pair of upright members.adjacent the upper ends 7 thereof, the ends of said transverse memberprojecting outwardly from the sides of said upright members, a pair ofbrace members pivotally mounted at the other end of said base member andextending to the upper ends of said upright members, shearable boltsserving to connect the intersecting upper ends of said upright membersand said brace members, said outward projections of said transversemember serving as abutment means extending into the planes of therespective brace members whereby on shearing of said shearable bolts,the upright members will pivot, the projections of the transverse memberengaging the brace members in the pivotal path thereof to pivot thebrace members causing collapse of the supporting structure.

6. An antenna supporting structure for a microwave radiator comprising,means providing a ground supported base, a pair of spaced apart uprightantenna supporting members pivotally mounted at their lower ends on saidmeans, a transverse member rigidly connecting said pair of uprightmembers'adjacent the upper ends thereof and extending outwardlytherefrom, a pair of inclined brace members pivotally mounted at theirlower ends on said means and extending upwardly to the upper ends ofsaid upright members, said outward extensions extendingrespectively intothe planes of the respective brace members, shearable pin means servingto connect the intersecting upper ends of said upright members and saidbrace members whereby on shearing of said pin means the supportingmembers pivot on the base means, the said outward extensions of itstransverse connecting member serving as abutment elements for engagementof the brace members and pivoting of the brace members rearwardly tocollapse the supporting structure.

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